Monitoring Reports

Potomac River flows continue to hold relatively steady. Less than an inch of precipitation is in the cumulative forecast for the basin over the next ten days.

Recent basin-wide average precipitation (above Little Falls):
(based on CO-OP's Low Flow Forecast System analysis of Middle Atlantic River Forecast Center (MARFC) gridded multisensor precipitation estimates)
Yesterday's area-weighted average basin precipitation: 0.14 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.23 (inches)

In the past 24 hours, up to 0.5 inches of rain fell in localized areas of the Potomac Basin, mainly in the northwestern portions and around the Washington D.C area. According to the Middle Atlantic River Forecast Center’s cumulative forecast, no substantial rain is expected in the next 72 hours. River flow at Point of Rocks increased slightly but is still close to the 2000 cfs daily monitoring threshold.

About 0.1 inches of rain fell in the Potomac Basin yesterday, mostly in the portion of the basin below Little Falls. The Middle Atlantic River Forecast Center’s cumulative forecast calls for 0.01 to 0.10 inches over the next 72 hours. River flow at Point of Rocks continues to remain below the 2000 cfs daily monitoring threshold.

Flow in the Potomac River at Point of Rocks continues to be close to the 2000 cfs threshold for CO-OP daily monitoring. Average precipitation yesterday in the watershed above Little Falls was 0.28 inches. The Middle Atlantic River Forecast Center’s cumulative forecast for the watershed over the next 3 days is just 0.01 to 0.10 inches.

Recent basin-wide average precipitation (above Little Falls):

Reinitiating CO-OP daily drought monitoring and reporting (Friday, 2023-07-28)

In the last 24 hours, MARFC reports precipitation ranging from 0.01 to 0.25 inches in portions of the Potomac watershed above Little Falls. The forecast for the next three days indicates a potential accumulation of up to 0.25-inch precipitation. (Note this is a correction to the emailed version.)

Despite the river flows at Point of Rocks being above the daily monitoring threshold of 2000 cfs, they remain relatively low for this time of year. Until a significant increase occurs, the CO-OP will continue daily monitoring to closely observe the situation.  

A little under a half inch of rain fell yesterday in Potomac watershed above Little Falls and up to ¼ inch is forecast over the next three days. Average river flow yesterday at Point of Rocks was just 2000 cfs, CO-OP’s threshold for daily monitoring. It’s likely that flows will rise slightly above this level over the next week due to the recent and forecasted rainfall. However, flows are low for this time of year, so CO-OP will continue daily drought monitoring until a significant increase occurs.

CO-OP is initiating daily drought monitoring and reporting today because Potomac River flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has fallen below 2000 cubic feet per second (cfs), CO-OP's daily monitoring threshold. According to the Middle Atlantic River Forecast Center (MARFC) quantitative precipitation forecasts, cumulative rainfall ranging from 1/10 to 3/4 inch is expected in the basin over the next 3 days. MARFC ensemble forecasts do predict additional rain and rising river flows over the next 10 days.

This is the final day of the three-day 2022 WMA Drought Exercise. Simulated Potomac River flows at Little Falls have fallen to 104 MGD. Forecasts for today indicate that SIMULATED flows are expected to rise. We requested a SIMULATED Jennings Randolph water supply release this morning of approximately 30 MGD with a Luke target of 297 cfs. Little Seneca continues to make a SIMULATED water supply release to augment flows at Little Falls.

This email concludes the 2022 Washington Metropolitan Area (WMA) drought exercise. A summary report describing exercise assumptions, activities, and tools will be prepared and published on ICPRB's website (www.potomacriver.org).